Keratins are a family of proteins found in the hair, skin, and other tissues of vertebrates. Hair is a unique source of human keratins because it is one of the few human tissues that are readily available and inexpensive. Although other sources of keratins are acceptable feedstocks for the present invention (e.g. wool, fur, horns, hooves, beaks, feathers, scales, and the like), human hair is preferred because of its biocompatibility in human medical applications.
Keratins can be extracted from human hair fibers by oxidation or reduction using methods that have been widely published in the art. If one employs a reductive treatment, the resulting keratins are referred to as kerateines. If an oxidative treatment is used, the resulting keratins are referred to as keratoses. These methods typically employ a two-step process whereby the crosslinked structure of keratins is broken down by either oxidation or reduction. In these reactions, the disulfide bonds in cystine amino acid residues are cleaved, rendering the keratins soluble without appreciable disruption of amide bonds. Many of the keratins can remain trapped within the cuticle's protective structure, so a second-step using a denaturing solution is typically employed to effect efficient extraction of the cortical proteins (alternatively, in the case of oxidation reactions, these steps can be combined). This step has also been widely published in the art as solutions such as urea, transition metal hydroxides, surfactant solutions, and combinations thereof have been employed. Common methods include the use of aqueous solutions of tris(hydroxymethyl) aminomethane in concentrations between 0.1 and 1.0M, and urea solutions between 0.1 and 10M.
Many protein purification techniques are known in the art and range from the most simplistic such as fractional precipitation, to the most complex such as immunoaffinity chromatography. For example, sub-families of acidic and basic keratins have been described as being separable by moving bounding electrophoresis, but these fractions or their properties have not been described.
The methods that have been described in the art to extract these proteins rely on a chemical process of oxidation or reduction with less than optimal extraction. Accordingly, there is a great need to provide an optimized protein extraction procedure that provides a highly pure keratin protein product that retains structure and function.